Field of the Invention
The present disclosure relates to an organic light emitting diode display and a method for driving the same.
Discussion of the Related Art
An organic light emitting diode (OLED) display includes a plurality of organic light emitting diodes (OLEDs) capable of emitting light by themselves and has many advantages, such as fast response time, high emission efficiency, high luminance, wide viewing angle, and the like.
An OLED serving as a self-emitting element includes an anode electrode, a cathode electrode, and an organic compound layer between the anode electrode and the cathode electrode. The organic compound layer typically includes a hole injection layer HIL, a hole transport layer HTL, an emission layer EML, an electron transport layer ETL, and an electron injection layer EIL. When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the hole transport layer HTL and electrons passing through the electron transport layer ETL move to the emission layer EML and form excitons. As a result, the emission layer EML generates visible light.
An OLED display includes a plurality of pixels, each including an OLED in a matrix and adjusts the luminance of the pixel based on a gray scale of video data. Each pixel includes a driving element, for example, a driving thin film transistor (TFT) for controlling an amount of driving current flowing in the OLED depending on a voltage applied between a gate electrode and a source electrode of the driving TFT. The electrical characteristics of the OLED and the driving TFT may vary depending on their operation temperatures or amounts of deterioration. For example, an operating voltage of the OLED, a threshold voltage and a mobility of the driving TFT, etc. may change because these elements deteriorate as their driving times increase. Further, the electrical characteristics of these elements may vary due to variations in manufacturing processes. These variations in the electrical characteristics of the OLEDs and/or the driving TFTs of the pixels may result in difference in the luminance of the pixels with respect to the same video data, thereby making it challenging to display a desired image.
Also, an IR drop may be generated in the OLED display due to the line resistance of a high potential power source. Thus, a magnitude of a high potential power voltage applied to each pixel line, which is typically connected to a plurality of pixels in a horizontal direction, on the display panel may vary depending on a separation distance between the pixel line and the high potential power source and result in deviation in the luminance of the pixel line, thereby also making it challenging to display a desired image.